1 . Field of the Invention
The present invention relates to the field of isolation systems and gravel pack assemblies for use in a wellbore. More particularly, the invention provides an improved system and method for zone isolation following gravel pack completions installed in a wellbore.
2. Description of the Prior Art
The present invention provides an isolation sleeve which is installed inside the production screen at the surface and thereafter controlled in the wellbore by means of an inner service string. In contrast, the prior art has used systems which involve intricate positioning of tools which are installed down-hole after the gravel pack.
These systems are exemplified by a commercial system available from Baker. This system utilizes an anchor assembly which is run into the wellbore after the gravel pack. The anchor assembly is released by a shearing action, and subsequently latched into position.
Certain disadvantages have been identified with the systems of the prior art. For example, prior conventional isolation systems have had to be installed after the gravel pack, thus requiring greater time and extra trips to install the isolation assemblies. Also, prior systems have involved the use of fluid loss control pills after gravel pack installation, and have required the use of thru-tubing perforation or mechanical opening of a wireline sliding sleeve to access alternate or primary producing zones. In addition, the installation of prior systems within the wellbore require more time consuming methods with less flexibility and reliability than a system which is installed at the surface.
There has therefore remained a need for an isolation system for well control purposes and for wellbore fluid loss control which combines simplicity, reliability, safety and economy, while also affording flexibility in use. The present invention satisfies this need, providing an isolation system which does not require the running of tailpipe and isolation tubing separately. Instead, the present system uses the same pipe to serve both functions: as tailpipe for circulating-style treatments and as production/isolation tubing.